When manipulating integrated circuits and other electronic devices or parts, an automated device handler is commonly used to pick up the device at one location and place it at another location for processing, storage, etc. The handler comprises a positioning mechanism that is moved by an actuator. The positioning mechanism picks up the device with a chuck that may rotate about the vertical axis of the handler. A chuck position sensor provides a signal corresponding to the absolute position and orientation of the chuck at any given time. The rotation of the chuck combined with the movement of the positioning mechanism enables the handler to pick up and deliver a device to any location, in any orientation, within the working space of the handler.
FIGS. 1-4 are simplified schematic drawings illustrating the operations performed by a device handler 10 as commonly used in the semiconductor industry. With reference to FIGS. 1A and 1B, the handler 10 has a positioning mechanism 12 that is designed to move throughout the working area of the handler. The positioning mechanism 12 has a vacuum chuck 26 at one end that is adapted to engage and then pick up devices 14 such as integrated circuits.
During operation, the positioning mechanism 12 picks up the device 14 from a first storage location 16. As shown in FIG. 3, the positioning mechanism 12 then delivers the device 14 to a destination 18, where the device is processed. After processing, the positioning mechanism 12 picks up the device 14 and delivers it to a second storage location 20. Before the positioning mechanism 12 can place the device 14 in the proper orientation at the destination 18, the handler 10 must determine the location and orientation of both the device 14 and the destination 18.
To determine the location and orientation of the device 14, the handler 10 need only determine the position and orientation of the device 14 relative to the chuck 26 since the chuck position sensor provides an indication of the position and orientation of the chuck 26. With reference to FIG. 2, the handler 10 determines the position and orientation of the device 14 with respect to the chuck 26 by rotating the chuck 26 between the two panels 42 of a conventional laser alignment system 40. The laser alignment system 40 can be installed on the positioning mechanism 12, or it can be fixed to the handler 10. Once the handler 10 has determined the relationship between the chuck 26 and the device 14, the handler 10 can place the device 14 in the proper orientation at the destination 18 if the position and orientation of the destination 18 is known. However, at this point, the handler 10 does not know the exact position and orientation of the destination 18. In some instances, the destination 18 is in the same plane as the first and second locations, and therefore the handler 10 needs only calibrate the position and orientation of the destination 18 in two dimensions, i.e. the x-y plane. In other instances, the destination 18 is non-planar with the first and/or second location and, therefore, the device 10 must be calibrated in three dimensions.
As mentioned above, the device 14 is delivered to the destination 18 for processing. One type of processing that is performed on some devices 14 is programming the device 14. For example, the device 14 may be a programmable read only memory ("PROM") that must be programmed prior to use. In such cases, the destination 18 includes a set of terminals, such as a socket, that mate with contacts, such as pins, on the device 14. The proper positioning and alignment between the device 14 and the destination 18 is critical to establishing the proper electronic contact between the contacts on the device 14 and the terminals at the destination 18. In order for the positioning mechanism 12 to deliver the device 14 to the destination 18 in the proper orientation, the handler 10 must first be calibrated. The calibration method, which is the subject matter of the present invention, is discussed in detail below, as is the conventional technique for calibrating the handler 10 for the position and orientation of the destination 18.
After the device is processed, the positioning mechanism 12 picks up the device 14 and places it onto another vacuum chuck (not shown), or in some instances a vacuum pedestal (not shown), of a marking apparatus 54, where the device is labeled or marked. The location of the chuck on the marking apparatus can stored in the handler's memory or can be calibrated by the system and method of the present invention, as described below. Finally, the positioning mechanism 12 picks up the device 14 and places it at the second storage location 20.
As explained above, before the positioning mechanism 12 can place the device 14 at the destination 18, the handler 10 must be calibrated so that the location and orientation of the destination 18 is known. The location of the devices 14 in the first storage area 16 must also be known. However, it is only necessary to know the general location of the devices 14 in the first storage area 16 since the chuck 26 can engage virtually any portion of each device 14. Thus, the general location of the devices 14 at the first storage location 16 can be permanently recorded in memory (not shown) in the handler 10. Similarly, the tolerance for placing the devices 14 at the second storage location 20 is relatively broad, so this general location 20 can also be permanently stored in the handler's memory. These locations can also be calibrated by the method of the invention, which is discussed below.
The tolerance for placing the devices 14 at the destination 18 can be very small, such as when the device 14 is an integrated circuit having many small, closely spaced terminal pins that must plug into a socket at the destination 18. In such cases, the exact location and orientation of the destination 18 must be determined. Furthermore, if the destination 18 is part of a removable module, the position and orientation of the destination 18 can change each time the module is installed or otherwise moved. Because the tolerance for insertion of an integrated circuit into a programming socket is extremely low, the exact location and orientation of the destination 18 must be established each time the module is moved. To establish these variables, the exact position and orientation of the destination 18 must be determined in a calibration procedure.
FIG. 4 shows the position and orientation of the destination 18 being calibrated according to the prior art calibration procedure. A video camera 22 is attached to the positioning mechanism 12 in a known relationship with the chuck 26 (The video camera was omitted from FIGS. 1-3 for purposes of clarity). The positioning mechanism 12 is manipulated until the video camera 22 is aligned with a predetermined location and orientation at the destination 18. Because the spatial relationship between the chuck 26 and the video camera 22 is stored in the memory of the handler 10, the handler 10 is able to determine the position and orientation of the destination 18 in the x-y plane of the handler 10 based on the position and orientation of the chuck 26 at that time. Thus, the position and orientation of the destination 18 is determined from signals provided by the chuck position sensor and data from the handler's memory indicative of the position and orientation of the video camera 22 relative to the chuck 26.
The handler 10 is able to determine when the video camera 22 is aligned with the destination 18 by examining a video image created by the video camera 22. In particular, the positioning mechanism 12 is manipulated until predetermined points on the video image (such as cross hairs) overlie predetermined markings at the destination 18. The handler could then align the device above the destination, and lower the device until it engaged with the destination.
Because video calibration does not calibrate the exact position of the destination with respect to the handler's z-axis, the handler must be designed to "feel" when the positioning mechanism 12 engages with the destination 18, or must store data corresponding to the position of the destination 18 along the z-axis. Since the video camera 22 and associated components serve no purpose other than calibrating the destination 18, the entire cost of the video camera 22 and components are added costs to the handler 10.
A need therefore exists for an improved system and method for calibrating the exact location and orientation of a destination for a device.